WASHINGTON — President Donald Trump said Tuesday that he had fired national security adviser John Bolton after a string of disagreements, removing one of the most hawkish voices in Trump's inner circle on a number of issues, including Taliban negotiations and China trade talks.

Trump announced on Twitter that he had asked for Bolton's resignation on Monday night, saying he had "disagreed strongly with many of his suggestions."

“I informed John Bolton last night that his services are no longer needed at the White House. I disagreed strongly with many of his suggestions, as did others in the Administration, and therefore I asked John for his resignation, which was given to me this morning,” Trump said on Twitter.

....I asked John for his resignation, which was given to me this morning. I thank John very much for his service. I will be naming a new National Security Advisor next week.

White House spokesman Hogan Gidley said that Trump had asked for Bolton's resignation on Monday night, and that it was delivered on Tuesday. White House press secretary Stephanie Grisham said Trump and Bolton had not spoken on Tuesday.

Bolton himself said in a tweet that he had offered to resign Monday night, and that the president had said in response that they would "talk about it tomorrow."

“I offered to resign last night," Bolton told NBC News via text. "He never asked for it, directly or indirectly. I slept on it, and resigned this morning.” He denied reports that he and Trump had gotten into a heated argument Monday night over the president’s plan to host Taliban leaders at Camp David.

Some National Security Council officials were caught off guard by Bolton’s firing, learning about it only when it flashed on TV screens.

Reports over the weekend that Bolton and Vice President Mike Pence disagreed with Trump's Camp David plan were the last straw for Bolton, according to two people familiar with the matter. On Monday, Pence tweeted that the stories were fake but Bolton did not — and that, according to the officials, upset Trump.

One person familiar with the breakdown between the two men said Trump didn’t want Bolton attending the U.N. General Assembly in New York with him later this month.

Asked if the disagreement over the Taliban talks led to Bolton’s dismissal, Grisham said “that there was no final straw."

"There were several issues," he said. "They had policy disagreements.”

But speaking on the condition of anonymity, one official said Afghanistan “broke open the bottom of the bag” in a relationship that had been eroding. Another official confirmed that sharp disagreement over the Afghanistan deal was the final issue that ruptured the relationship.

Bolton, known as a fierce infighter, had few loyal allies internally. He had clashed with many senior members of the administration at times, including Pence and Secretary of State Mike Pompeo.

But he could also build alliances when needed. He worked closely with Pence on multiple issues, including efforts to replace Venezuelan leader Nicolás Maduro, and aligned with Pompeo on encouraging a hard-line stance on China, said a former administration official.

He was one of the loudest hawks inside the West Wing, perpetually skeptical of the country's adversaries and unafraid of the prospect of military conflict. Few others in the upper ranks of the administration were as deeply versed in the nuances of foreign policy, a void that Pompeo will now have an outsize role in filling — particularly when it comes to Iran, China and Venezuela, said the former official.

Most recently, the two had sparred over Trump's desire to have leaders of the Taliban visit Camp David in the days before the anniversary of the Sept. 11, 2001, terrorist attacks to finalize peace talks. The idea was strongly opposed by Bolton, even as officials at the State Department argued it could move the parties closer to an agreement, officials said.

Bolton had been deeply skeptical of negotiations with the Taliban. U.S. negotiators have been working under the president’s demand that a drawdown occur before November 2020, when he’s up for re-election.

Asked if he had been startled by Bolton's quick exit, Pompeo told reporters he had not. "I'm never surprised. And I don’t mean that on just this issue," he said.

Bolton’s departure could pave the way for a more flexible approach by the Trump administration on North Korea, Iran, Venezuela and Afghanistan, former U.S. officials and two current U.S. officials said.

Bolton had pushed Trump to take a harder line on other regimes he has deemed untrustworthy. Trump, on the other hand, campaigned on the promise to get the U.S. out of conflicts.

While Bolton had previously pushed for striking Iran in an effort at regime change, Trump has indicated he would like to sit down with Iranian officials, and that regime change is off the table; Pompeo confirmed Tuesday that the president is likely to speak with Iranian President Hassan Rouhani when the U.N. General Assembly meets in New York. "The president has made it very clear, he’s prepared to meet with no preconditions," said Pompeo.

Some officials in the administration had also grown frustrated with Bolton’s stance on Venezuela, in which he pushed for the imposition of harsh sanctions on the Maduro regime and opposed renewing a waiver to allow the energy company Chevron to keep operating in the country.

When asked earlier about his differences with Bolton, Trump indicated he didn't have a problem with his national security adviser giving an opinion that diverged from his own.

"I have some hawks," the president said in a "Meet the Press" interview this summer. "Yeah, John Bolton is absolutely a hawk. If it was up to him he'd take on the whole world at one time, OK? But that doesn't matter, because I want both sides."

Bolton has had his fair share of detractors in Congress. Many of those critics praised his departure — with even some who held a favorable view of him said the change could be a positive one.

“I like John Bolton, I think he sees the world for what it is. I've always had a similar view of threats that we face,” said Graham, R-S.C. “But the personal relationship between the president and national security adviser is important. I think the view that there’s some public discussions about Bolton being on the other side of meeting with the Taliban probably was a bridge too far.”

But Sen. Mitt Romney, R-Utah, said Bolton’s departure was a “huge loss” for the country.

"His view was not always the same as everybody else in the room, that’s why you wanted him there,” Romney told reporters. “The fact that he was a contrarian from time to time is an asset, not a liability.”

This is the third national security adviser that Trump will have to replace. His first, Michael Flynn, was in court for a status hearing on Tuesday before his sentencing for lying to U.S. officials. Flynn's successor, Army Lt. Gen. H.R. McMaster, said he was retiring after repeated disagreements with Trump.

It is unclear what will now happen with the team of foreign policy experts Bolton had built over more than a year — a state of affairs adding yet more instability to the national security ranks under Trump's presidency.

Trump named Bolton, the former U.S. ambassador to the United Nations and undersecretary of state for international security, to the post in a tweet in March 2018. At the time of his appointment, Bolton said in a Fox News interview that he was taken off guard.

Trump said Tuesday that he would name a new national security adviser next week. Gidley said Tuesday afternoon that deputy national security adviser Charlie Kupperman would replace Bolton as the acting national security adviser.

Among those being considered as Bolton's permanent replacement, Sen. Lindsey Graham said on Fox News Thursday, are Ricky Waddell, a former deputy national security adviser who is currently assistant to the chairman of the Joint Chiefs of Staff; Brian Hook, a seasoned diplomat who is now the State Department’s point person on Iran; and Keith Kellogg, the national security adviser to the vice president.

"Those are three names the president mentioned to me," Graham said. "There are others on the list, but what are we looking for? Somebody that can work with Pompeo, work with the Department of Defense to get the inner agency back — stood back up."

Hours before Trump announced his departure, Bolton sent a final public warning on Iran.

"Now that we're two weeks from #UNGA, you can be sure #Iran is working overtime on deception," Bolton wrote in a tweet. "Let's review the greatest hits, starting with the most recent. #Iran denied the Adrian Darya-1 was headed to #Syria, then confirmed today its oil was offloaded there. #IranWebOfLies"

Shannon Pettypiece

Shannon Pettypiece is the senior White House reporter for NBCNews.com.